Android 使用 LinearGradient 实现对角线颜

Android 使用 LinearGradient 实现对角线颜色渐变

package com.demo.lib.view

import android.content.Context
import android.graphics.*
import android.util.AttributeSet
import android.util.Log
import android.widget.FrameLayout
import com.okay.lib.R

/**
 * Create by shadow
 * 负责给view或是viewG添加渐变背景色
 *
 *  //Avoid object allocations during draw/layout operations (preallocate and reuse instead)，意为避免在绘制/布局中去实例化对象。
@SuppressLint("DrawAllocation")
 */
class GradientViewGroup @JvmOverloads constructor(
    context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0
) : FrameLayout(context, attrs, defStyleAttr) {

    private val paint: Paint = Paint()

    private val rect :RectF = RectF()

    /**
     * 圆角
     */
    private val radius = 10F

    private var linearGradient: LinearGradient? = null

    init {
        paint.isAntiAlias = true
        Log.d("GradientViewGroup", "measuredWidth = $measuredWidth")
    }

    override fun dispatchDraw(canvas: Canvas) {
        super.dispatchDraw(canvas)
        linearGradient = LinearGradient(
            0F,
            0F,
            measuredWidth.toFloat(),
            measuredHeight.toFloat(),
            resources.getColor(R.color.colorAccent),
            resources.getColor(R.color.colorPrimary),
            Shader.TileMode.CLAMP
        )
        rect.set(0F, 0F, measuredWidth.toFloat(), measuredHeight.toFloat())
        paint.shader = linearGradient
        Log.d("GradientViewGroup", "measuredWidth = $measuredWidth")
//        canvas.drawRect(rect, paint)
        canvas.drawRoundRect(rect,radius,radius,paint)
    }
}